1. Field of the Invention
The invention is directed to a torsional vibration damper, in particular for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine. The torsional vibration damper includes a disk-shaped first damper part, a second damper part which is rotatable about an axis with respect to the first damper part, and a torsion bar device or torsion spring device with at least one torsion spring unit.
2. Description of the Prior Art
Torsional vibration dampers of this kind are used, for example, in clutch disks in order to enable damping of torsional vibrations occurring in the power transmission path between an internal combustion engine and the driving wheels of a vehicle. A clutch disk with a known torsional vibration damper is shown in FIG. 12. This known clutch disk 8s comprises a hub 10s which is mountable, for example, on a transmission input shaft so as to be displaceable in the longitudinal direction of the shaft, but is fixed with respect to rotation about an axis A with the transmission input shaft. A hub disk 12s is fixed on the hub 10s, e.g., by welding or the like. A driver disk 14s is arranged in the axial direction on one side of the hub disk 12s. A cover plate 16s is arranged on the opposite side of the hub disk 12s and is fixed with the driver disk 14s by a plurality of bolt elements 18s. The driver disk 14s is connected in the radial inner region with a bearing ring 20s so as to be fixed with respect to rotation relative thereto. The bearing ring 20s is rotatably supported on the hub 10s. A plate spring 22s is arranged between the hub disk 12s and the cover plate 16s and pretensions the input part of the clutch disk 8s in the axial direction, which input part is formed of the driver disk 14s and cover plate 16s, so that the bearing ring 20s contacts the hub disk 12s with pretensioning, possibly with the intermediary of friction linings or the like. In a radial outer region, the driver disk 14s is coupled with friction linings 24s which can be clamped in a manner known per se between a flywheel and a contact pressure plate of a motor vehicle clutch for transmitting torque.
Circumferentially extending spring windows 26s, 28s, 30s are provided in the hub disk 12s, the driver disk 14s and the cover plate 16s. A spring 32s is arranged in the spring windows 26s, 28s, 30s. The ends of the spring 32s contact control edges 34s, 36s, 38s of the hub disk 12s or of the driver disk 14s and the cover plate 16s, the ends being located opposite one another in the circumferential direction. Due to the spring 32s, the hub disk 12s is pretensioned in a predetermined rest position with respect to the driver disk 14s and the cover plate 16s. When torque occurs, the spring 32s is compressed so that rotation can occur between the hub disk 12s and the driver disk 14s and cover plate 16s. The spring 32s cooperates with the bearing ring 20s which contacts the hub disk 12s accompanied by pretensioning in order to damp torsional vibrations in a manner known per se. In clutch disks of this type, a plurality of springs are arranged in succession in the circumferential direction in windows provided in a suitable manner, although this is not shown in FIG. 12.
The problem in torsional vibration dampers of this kind is that the springs must have a sufficiently large spring constant on the one hand and an adequate spring length on the other hand in order to provide good and defined damping characteristics. However, if the spring length is too great, the springs tend to expand outward in their radial center regions due to their pretensioning. In so doing, they contact the respective outer rims of the spring windows in the hub disk or the driver disk and cover plate, so that the friction in the torsional vibration damper constructed in this way is appreciably increased due to this contact. Since this frictional force depends upon the extent of compression of the spring, its contribution to the friction moment provided between the hub disk and the driver disk and cover plate can be calculated only with difficulty and this frictional force should accordingly be prevented.
A torsional vibration damper with an amplitude-dependent friction moment is known from the German Patent DE 34 31 809. In this known torsional vibration damper there is also a hub disk arranged in the axial direction between a driver disk and a cover plate. Spring windows for receiving springs are again formed in the hub disk and the driver disk and cover plate. In particular, for this purpose, two springs following one another in the circumferential direction are arranged in the corresponding spring windows in the hub disk and the driver disk and the cover plate and accordingly form a torsion spring unit. The torsion spring unit constructed in this way again contacts control edges of the spring windows in the hub disk or the driver disk and the cover plate by its ends which are arranged at a distance from one another in the circumferential direction. A spring contact arm of an intermediate disk is arranged between the ends of the spring which face one another. In order to provide the amplitude-dependent friction moment in this known torsional vibration damper, a first friction device is provided, on the one hand, which acts directly between the hub disk and the driver disk and cover plate. On the other hand, a second friction device is provided which acts between the intermediate disk and the driver disk. Accordingly, one of the two springs of the torsion spring unit is bridged by the second friction arrangement depending upon the torque transmission direction.
Another problem in this known torsional vibration damper is that the torsion spring unit formed by the two springs contacts an outer edge of the spring window formed in the hub disk or the driver disk and cover plate substantially along its entire outer circumferential surface, especially due to its pretensioning. In this known torsional vibration damper, also, this leads to the disadvantage that an additional friction moment which can be calculated only with difficulty is generated in the torsional vibration damper due to the pretensioning of the torsion spring unit which accordingly occurs in the radial outward direction.
Accordingly, it is an object of the present invention to provide a torsional vibration damper, especially for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine, in which the occurrence of unintended friction moments is prevented.
In accordance with a first aspect of the present invention, this object is met by a torsional vibration damper, especially for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine, comprising a disk-shaped first damper part, a second damper part which is rotatable about an axis with respect to the first damper part, and a torsion spring device with at least one torsion spring unit. The at least one torsion spring unit comprises at least two springs which are arranged substantially following one another in the circumferential direction. Ends of the torsion spring unit, which are directed opposite to one another in the circumferential direction, cooperate with the first damper part and second damper part with respect to operation for damping torsional vibrations. The damper further includes at least one intermediate ring element which is rotatable about the axis with respect to the first damper part and the second damper part and with at least one spring contact arm for the at least one torsion spring unit. The spring contact arm extends substantially radially with respect to the axis and is arranged in the circumferential direction between ends of the at least two springs of the at least one torsion spring unit, which ends face one another. The at least one intermediate ring element further comprises radial movement restraining means for protecting the at least two springs against movement in the radial outward direction in their end regions facing the at least one spring contact arm.
In the torsional vibration damper according to the invention, the torque between the first damper part and the second damper part is transmitted by a torsion spring unit formed of at least two springs. This means that the torsion spring unit has a distinctly greater length and can accordingly also provide better damping characteristics compared with known springs which are often constructed with only a short length due to the problems described above. However, due to the use of shorter springs which together can form a torsion spring unit, the problem of the deflection of the springs in the radial outward direction can be prevented to a great extent. Additional assistance is provided in that the springs of the torsion spring unit contact the spring contact arm of the intermediate ring element by their end regions which face one another and are prevented from executing a deflecting movement radially outward by the radial movement restraining means. This means that each of the springs of the torsion spring unit contacts either the first damper part or the second damper part or the spring contact arm of the intermediate ring element only in the region of its ends which are oppositely directed in the circumferential direction. An outwardly directed deflecting movement of the individual springs and the frictional force which occurs in so doing is therefore prevented by contact at the first damper part and/or second damper part.
According to a second aspect of the present invention, a torsional vibration damper, especially for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine, comprises a disk-shaped first damper part, a second damper part which is rotatable about an axis with respect to the first damper part, and a torsion spring device with at least one torsion spring unit. The at least one torsion spring unit comprises at least three springs which are arranged substantially so as to follow one another in the circumferential direction. Ends of the torsion spring unit which are oppositely directed in the circumferential direction cooperate with the first damper part and the second damper part with respect to operation for damping torsional vibrations. The damper further includes at least two intermediate ring elements which are rotatable about the axis with respect to the first damper part and second damper part and with respect to one another. Each of the ring elements has at least one spring contact arm for the at least one torsion spring unit, which spring contact arm extends substantially radially with respect to the axis. A spring contact arm of an intermediate ring element is arranged in each instance in the circumferential direction between ends of successive springs of the at least one torsion spring unit, which ends face one another.
In such a configuration of the torsional vibration damper according to the invention, the total spring path of every torsion spring unit can be increased by providing more than two springs. However, this does not result in a lengthening of the springs; rather the relatively short springs are supported against one another with the intermediary of the spring contact arms of the respective intermediate ring elements. Accordingly, the springs are again prevented from excessive bulging in the radial outward direction in their center regions due to centrifugal force occurring during operation and are accordingly prevented from coming into contact with other structural component parts.
In a further embodiment of the torsional vibration damper according to the invention, each intermediate ring element further comprises radial movement restraining means for securing the springs against a radially outward movement in their end regions facing the respective spring contact arm.
In still another embodiment of the present invention, every intermediate ring element comprises an inner ring portion arranged radially inside the at least one torsion spring unit or/and an outer ring portion arranged radially outside of the at least one torsion spring unit. The at least one spring contact arm extends away from the inner and outer ring portion substantially in the radial direction.
Control edges for the contact of the springs are advantageously provided at the ends of the at least one spring contact arm at every intermediate ring element, which ends are oppositely directed in the circumferential direction. For this purpose, the radial movement restraining means can be formed by projections which extend away substantially in the circumferential direction from the at least one spring contact arm in a radially outer end region of the control edges.
In order to ensure that the spring force of the at least one torsion spring unit is transmitted in a suitable manner in a plane orthogonal to the axis and such that no tilting moment is generated between the individual structural component parts, in another embodiment of the invention a spring window is provided in the first damper part for the at least one torsion spring unit. A corresponding spring window for the at least one torsion spring unit is provided in the second damper part. Control edges for the contact of the ends of the torsion spring unit which are oppositely directed in the circumferential direction are formed at the ends of the spring window in the first damper part and in the second damper part, which ends are oppositely directed in the circumferential direction. The at least one spring contact arm of every intermediate ring element lies with at least some areas of its radial portion in the axial direction, which radial portion is provided for contacting the springs, in a common plane orthogonal to the axis with the control edges formed at the spring window of the second damper part. For example, every spring contact arm is curved in its region which is connected with the inner ring portion and/or outer ring portion such that the inner ring portion and/or outer ring portion are/is displaced in the axial direction with respect to the second damper part and does not overlap the latter axially.
If the inner ring portion and/or outer ring portion can be brought into contact with an axial lateral surface of the second damper part, the intermediate rings can be secured against axial displacement by means of the respective ring portions in cooperation with the second damper part.
In order to make use of the entire radial extension of the respective spring window in the second damper part for the springs to contact the respective spring contact arms by resting against the latter, in a further embodiment the curved region of every spring contact arm is constructed near radial inner ends regions or radial outer end regions of the spring window in the second damper part. Accordingly, further, radial movement restraining means are formed for the intermediate ring elements by the curved regions which are formed near the respective end regions of the spring window and which contact the damper part when the respective spring arms and accordingly the intermediate ring elements are displaced radially.
Further, when the radial extension of every intermediate ring element is smaller than the radial extension of the spring window, it is ensured that the intermediate ring elements take up as little installation space as possible so that more space is available for other parts. Additionally, interference between the intermediate ring elements and other structural component parts can be prevented.
It is advantageous, particularly when a plurality of intermediate ring elements are provided, if the curved regions of a spring contact arm of a first intermediate ring element are curved axially in the opposite direction with respect to the curved regions of a spring contact arm of another intermediate ring element. In a configuration of this kind, the respective inner and outer ring portions of the intermediate ring elements contact sides which are directed opposite one another in the axial direction with respect to the second damper part, so that the intermediate ring elements cannot interfere with one another.
Alternatively or in addition, the curved regions of a spring contact arm of a first intermediate ring element can be curved axially in the same direction with respect to the curved regions of a spring contact arm of another intermediate ring element. This is advantageous particularly when more than two, e.g., three, intermediate ring elements are provided. In particular, the radial extension of one of the intermediate ring elements can then be smaller than that of the other respective intermediate ring element such that the outer ring portion of the intermediate ring element is arranged with the smaller radial extension radially inside of the outer ring portion of the other respective intermediate ring element and/or the inner ring portion of the intermediate ring element is arranged with the smaller radial extension radially outside of the inner ring portion of the other respective intermediate ring element. As a result, the respective intermediate ring elements whose curved regions are curved on the same side are nested radially one inside the other, so that even when a plurality of intermediate ring elements are provided, e.g., three intermediate ring elements, no interference can occur.
In order to be able to make very effective use of the circumferential length of every torsion spring unit, it is suggested that every intermediate ring element have only one outer ring portion and that every spring contact arm be constructed as a contact wedge which substantially tapers to a point radially inwards. In a configuration of this kind, every spring contact arm constructed as a contact wedge is formed so that it tapers to a point in its radial inner region, since it need not be connected with an inner ring portion. This means that the circumferential extension of every spring contact arm can be reduced so that control edges which are provided at the latter lie closer to one another in the circumferential direction. Consequently, there is more installation space available for springs of every torsion spring unit and the effective spring length can accordingly be lengthened.
Also, in order to be able to ensure a reliable and trouble-free operation in a configuration of this type it is suggested that the outer ring portion be reinforced.
In an advantageous manner, every intermediate ring element comprises at least the inner ring portion and the inner ring portion is arranged adjacent to the radial inner region of the damper part in the axial direction.
In a further embodiment of the invention, every intermediate ring element is curved in the region of the at least one spring contact arm, from the inner ring portion radially outward in the axial direction toward the second damper part. When the second damper part is constructed so as to be substantially planar, the second damper part can be punched, e.g., as a metal plate or the like, without the need for additional forming processes.
Alternatively, the second damper part can be curved radially outward in the axial direction toward the at least one intermediate ring element in its radial region corresponding to the at least one spring contact arm. The contact points of the springs at the second damper part and the spring contact arm can accordingly be displaced in an improved manner in a common plane orthogonal to the axis.
Alternatively, it is also possible that the at least one intermediate ring element is constructed in a substantially planar manner and that the second damper part is curved radially outward in the axial direction toward the intermediate ring element in its radial region corresponding to the spring contact arm.
In order to provide a symmetrical torque transmission between the first damper part and second damper part, the first damper part comprises a first disk element which is arranged adjacent to the second damper part in axial direction and a second disk element which is arranged in axial direction on the side directed opposite to the first disk element with respect to the second damper part and is preferably fixedly connected in a radially outer region with the first disk element. In so doing, the inner ring portion and/or the outer ring portion of each intermediate ring element is axially arranged between the second damper part and the first disk element or the second disk element of the first damper part. In a configuration of this type, an axial guiding of the at least one intermediate ring element is provided at the same time.
Further, the first disk element can be connected in a radially inner region with a bearing ring element so as to be fixed with respect to rotation relative thereto. The inner ring portion of the at least one intermediate ring element is arranged between the first disk element and the second damper part.
In the normal operating state, the at least one intermediate ring element is held in a centered manner with respect to the first damper part and the second damper part and the axis by means of the springs of the at least one torsion spring unit and the occurring spring force deflecting action in the region of the spring contact arm. The springs contact the at least one spring contact arm and the radial movement restraining means. However, in order to prevent a lateral deflection of the at least one intermediate ring element in the event of malfunction, e.g., a damaged spring, the bearing ring element has a ring portion extending axially between the first disk element and the second damper part. The ring portion forms an emergency guide for the inner ring portion of the at least one intermediate ring element at its outer circumferential surface.
To provide a defined torsional vibration damping force, a friction arrangement can be provided which acts between the second damper part and the first damper part for providing the torsional vibration damping frictional force. For this purpose, the bearing ring element, for instance, can contact the second damper part in the axial direction, possibly with the intermediary of the friction lining means, and a spring arrangement provided between the second damper part and the second disk element can pretension the bearing ring element in the direction of the second damper part. Alternatively, the second disk element, possibly with the intermediary of friction lining means, can contact the second damper part in the axial direction. A spring arrangement provided between the second damper part and the bearing ring pretensions the second disk element in the direction of the second damper part.
In a particularly simple and economical embodiment, the spring arrangement comprises a spring element formed by a plate spring, a ring spring, a wave spring or the like.
For this purpose, an additional defined friction moment can be provided if the spring element contacts the second damper part in a radial inner region and engages with at least one axially directed projection in a corresponding recess in the radial inner region of the second damper part. This means that the spring element is fixed with respect to rotation relative to the second damper part and provides a defined friction moment when torsional vibration occurs with corresponding relative rotation between the first damper part and the second damper part by means of the friction contact with the first damper part.
To prevent the springs of the at least one torsion spring unit from being fully compressed, i.e., to their minimum length, rotational path limiting means are provided for limiting the rotational path between the first damper part and the second damper part. For this purpose, the rotational path limiting means at the first damper part and at the second damper part can comprise stop means acting in the circumferential direction. The stop means at the first damper part can act directly on the stop means at the second damper part.
Alternatively, first stop means cooperating with the stop means at the first damper part can be provided at every intermediate ring element and second stop means cooperating with the stop means at the second damper part and/or with the stop means at another intermediate ring element can be provided. This is especially advantageous when the springs of the at least one torsion spring unit have different spring constants. In such a case, a stepped spring force can be provided by the torsion spring unit.
In so doing, the first and second stop means of every intermediate ring element can be formed, for example, by substantially radially directed stop faces which are formed at projections that, per se, extend away from the at least one spring contact arm in the circumferential direction.
In a particularly simple construction, the stop means at the first damper part is formed by at least one pin element connecting the first disk element with the second disk element. Accordingly, the use of additional structural component parts for forming the stops is avoided.
The stop means at the second damper part can be formed by substantially radially extending stop faces provided in a radially outer region of the second damper part.
The springs of the at least one torsion spring unit can have the same spring constants. Alternatively, the springs of the at least one torsion spring unit can have different spring constants, so that a stepped spring response of the at least one torsion spring unit can be obtained as was mentioned above.
In modern automotive engineering, clutch units comprising a flywheel, clutch disk, contact pressure plate assembly and clutch casing are often produced and sold in a preassembled manner. Such clutch units must then be attached to an end face of a crankshaft by means of screw bolts which penetrate the flywheel. In order to enable screws to be introduced through the flywheel through a clutch unit of this type which can contain a torsional vibration damper according to the invention, e.g., as a clutch disk, the spring window in the second damper part is constructed to extend farther radially inward than the corresponding spring window in the first and second disk parts of the first damper part. Axial through-openings which are aligned in the axial direction are provided in the first and second disk parts in a region corresponding to the portion of the spring window in the second damper part, which portion is lengthened radially inward. This is advantageous particularly in relation to the torsional vibration damper according to the invention, since the at least one torsion spring unit can be lengthened radially inward due to the construction of the at least one torsion spring unit with short springs and can accordingly extend in the radial region in which the screw bolts are provided for fastening the flywheel to the crankshaft.
The torsional vibration damper according to the invention can be constructed in such a way that the first damper part or the second damper part comprises an input part of a clutch disk, especially a driver disk, and so that the other respective part comprises an output part of a clutch disk, especially a hub disk.
In an embodiment which is simple and economical to produce, the part of the first damper part and second damper part forming the output part can be fixedly connected with a hub, preferably by welding or the like. The bearing ring can then be mounted on the hub so as to be rotatable about the axis.
According to a third aspect of the present invention, a torsional vibration damper, especially for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine, comprises a disk-shaped first damper part, a second damper part which is rotatable about an axis with respect to the first damper part, and a torsion spring device with at least one torsion spring unit. The at least one torsion spring unit comprises at least two springs which are arranged substantially so as to follow one another in the circumferential direction. The ends of the torsion spring unit, which are oppositely directed in the circumferential direction, cooperate with the first damper part and the second damper part with respect to operation for damping torsional vibrations. At least one intermediate ring element is rotatable about the axis with respect to the first damper part and the second damper part. At least one spring contact arm for the at least one torsion spring unit extends substantially radially with respect to the axis. The at least one spring contact arm is arranged in the circumferential direction between ends of at least two springs of the at least one torsion spring, which ends face one another. The disk-shaped first damper part comprises a first disk element and a second disk element which is arranged at a distance axially from the first disk element and is fixedly connected therewith. The second damper part is constructed substantially in the manner of a disk and is arranged between the first disk element and the second disk element in the axial direction. The at least one intermediate ring element lies in a common plane with the second damper part, which plane lies substantially orthogonal to the axis, at least in the region of its spring contact arm for every torsion spring unit.
A construction of this kind ensures that the force transmission between the second damper part and the spring contact arm of every intermediate ring element, which spring contact arm is associated with every torsion spring unit, occurs in a plane orthogonal to the axis, i.e., the occurrence of tilting moments is extensively prevented in every torsion spring unit while taking up little space in the axial direction.
A torsional vibration damper which is constructed in a particularly simple manner and takes up only little axial installation space can be obtained when ever intermediate ring element is formed only by a single disk part.
The quantity of intermediate ring elements which are rotatable relative to one another is advantageously smaller by one than the quantity of springs of each torsion spring unit, and each intermediate ring element then advantageously has a spring contact arm for every torsion spring unit. Since the quantity of limiting surfaces formed between the springs of a torsion spring unit is smaller by one than the quantity of respective springs, precisely one intermediate ring element is accordingly provided with its associated spring contact arm for every limiting surface. Accordingly, the quantity of structural component parts can be kept as low as possible by more than two springs for every torsion spring unit.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.